The invention relates to improvements in implements for facilitating introduction of slender elongated flexible medical devices (such as rotary or other catheters or cardiac pacemaker electrodes) into cavities of animal bodies. More particularly, the invention relates to improvements in implements or instruments which can be utilized to advance elongated flexible medical devices along a complex path, especially from one or more wider passages into one or more narrower passages in a human heart or in another organ or part of an animal body.
When the working end of a rotary or other catheter must be introduced into a selected portion of an animal body by way of one or more blood vessels and/or other passages, it is often necessary to change the direction of advancement of the distal end of the catheter, for example, at the junction of a wider blood vessel with a narrower blood vessel which latter is inclined relative to the adjacent portion of the wider vessel. Heretofore known implements which are used to facilitate introduction of catheters include elongated flexible sleeves which are made of a plastic material. The sleeves can be used for introduction of the leading or distal end of a rotary dilatation catheter into a human heart. To this end, a plastic sleeve is introduced into a relatively large blood vessel which leads to the heart and communicates with one or more narrower vessels (branch passages). The distal end of the sleeve is positioned at the junction of the wider vessel with the narrower vessel, and the catheter is thereupon advanced in the inserted sleeve so that its distal or working end emerges from the distal end of the sleeve at the junction. The main purpose of the sleeve is to ensure that the working end of the catheter cannot contact and possibly injure the tissue around the wider passage while the working end of the catheter advances toward the junction. A rotary dilatation catheter is described and shown, for example, in published German patent application No. 35 32 653.
The aforediscussed conventional sleeve is of no help in introducing the distal end of the catheter from the wider into the narrower passage in an animal body, e.g., in a human heart. Thus, the sleeve does not and cannot assist the distal end of the catheter in finding its way from a wider passage into a narrower passage which is inclined relative to (e.g., which makes an acute angle with) the wider passage and must be entered by the distal end of the catheter. This problem of causing the distal end of a flexible catheter to make a sharp curve (e.g., a U-curve) on its way toward an obstruction in a relatively narrow passage in a human heart or in another organ or part of an animal body remained unsolved for many decades.
Attempts to steer the distal end of a catheter along an elongated path which has two or more mutually inclined portions include the utilization of pull strings (e.g., thin filaments) which are manipulated to change the orientation of the distal end at the junction of two mutually inclined passages. The pull strings are effective to direct the distal end of a flexible catheter toward the junction of two mutually inclined blood vessels or other passages in an animal body. However, the pull strings also exhibit a number of drawbacks, particularly as concerns the space requirements of the sleeve which confines the catheter and the strings. Thus, the wall thickness of the sleeve must suffice to provide channels for the pull strings. A relatively thick-walled sleeve cannot be readily flexed which creates problems in connection with introduction of the sleeve even into a larger blood vessel or another passage in an animal body. Moreover, a relatively stiff sleeve cannot permit a pronounced change of orientation of its distal end for the purpose of steering the distal end of a catheter into the inlet of a narrower passage which is inclined (e.g., at a relatively small acute angle) relative to a wider passage. It has been found that a sleeve which is capable of accommodating one or more pull strings to change the orientation of its distal end cannot be used for introduction of catheters into relatively narrow passages in a human heart or another organ. If the outer diameter of such sleeve is sufficiently small to permit insertion into a relatively narrow passage in a human heart, the inner diameter of the sleeve is much too small to permit introduction of a rotary or other dilatation catheter. A tubular guide with pull strings is disclosed in German Pat. No. 38 19 372 to Zeiher.
U.S. Pat. No. 3,749,085 to Willson et al. discloses a vascular tissue removing device which is formed by a multi-strand coil of wires. The ends of the wires are cut to define axially projecting radially offset cutters. Remote control means is provided to guide the tissue removing device.
U.S. Pat. No. 4,020,829 to Willson et al. discloses an instrument which employs a guide wire having a short flexible distal section connected with a relatively long multi-wire axial and rotary torque transmitting section. The purpose of the guide wire is to steer a soft, thin-walled flexible tubular catheter through the compound curves involved in the junctions between various arterial branches. The inserted tubular catheter is used for introduction of a fluid into a remote internal body passageway. The single-wire distal section of the guide wire is soldered to the multiple-wire proximal section. This guide wire can be said to constitute a flexible core for guidance of a tubular implement which surrounds the core during introduction into an arterial branch.